This invention concerns the wiping means of the windows of motor vehicles and, more specifically, their wear.
A wiper blade equipped with its elastic wiper stem is a piece of the vehicle that wears out and which must be replaced regularly if one wants to guarantee a good wiping quality of the window. This proves to be even more important for the driving safety while one is using the wiper blade on the front windshield of the vehicle.
The sources of wear are numerous and the blade is susceptible to degrading as much at the level of the wiper stem as at the joints and the articulation mount that carries it.
For example, the wiper stem is susceptible to wear via friction but can also wear due to the deterioration of the material that it is made of.
The agents of such deterioration are principally:
sun light, and more specifically, ultraviolet rays that light contains;
oxygen because, even if the vehicle is normally parked in a closed garage, and thus sheltered from sunlight, it cannot be sheltered from oxidation;
temperature, variations of temperature, and humidity;
ozone and all electromagnetic radiation from the environment.
Thus, it appears to be pertinent to determine the lifespan of the wiper blade as a function of its time exposed to the air.
In addition, frequently drivers are incapable of remembering when they last changed their wiper blades. In effect, such an operation is not generally entrusted to a vehicle repair specialist who can, for example, proceed to a systematic, regular replacement of the blades.
It is known, for example, from application WO/01896, to use wear indicators that change color as a result of exposure to the environment. This type of indicator presents the major inconvenience of only being sensitive to one parameter of wear, for example ultraviolet rays.
The goal of this invention is to allow the driver to determine the state of reliable wear of the wiper blades of his vehicle via a wear indicator that is representative of real wear constraints, and not dependent on sun exposure, that is to say the geographic or meteorological situation, or environment, for example pollution or altitude.
In order to achieve this goal, the invention proposes taking into account, in the composition of the wear indicator, the principal agents or parameters of the wear of the wiper stem of the wiper blades and their combined action in use conditions.
More precisely, the goal of the invention is a motor vehicle wiper comprising a wiper blade that is mounted on the free end of a wiper stem and pressing a wiper stem against a window to be wiper, in which the wiper is provided with an indicator comprising a substance based at least on an azo compound.
It has been remarked that the sensitivity of the azo compounds to chemical (oxygen, ozone) and physical conditions (radiation, temperature, humidity) as well as to mechanical constraints is comparable to that of the elastamers making up the wiping stem.
According to other characteristics of the invention;
the wear indicator is a multi-layered label comprising an adhesive layer and a plastic support film from at least one inert layer of a reference color and a reactive degradable layer, made up of a substance of a different color based on the azo compound;
the inert and reactive layers are formed via ink in which an inert chemical pigmentation, defining a reference color, and a base organic pigmentation from the azo by-products are respectively created;
the inks are successively placed on the plastic support via silk-screening;
the plastic support is in polyvinyl, polypropylene, or polyester and is covered with a protective layer fixed to the support film, in a detachable manner, via a semi-porous adhesive, this layer being pulled back during the mounting of the blade on the vehicle.
the wear indicator is carried by the wiper blade.